1. Field of the Invention
This invention relates to thin-film heads which are used for the perpendicular magnetic recording and reproduction of data or information in apparatus such as a computer, tape or videotape recorder.
2. Description of the Prior Art
Thin-film magnetic heads for perpendicular magnetic recording are generally suitable for use in making high density magnetic recordings since they form a very small magnetic circuits. They include a magnetic thin film having a high permeability and a high saturation magnetic flux density. As a thin-film magnetic head is made by a manufacturing process based on semiconductor technology, it can be made at a low cost, yet it has a high degree of dimensional accuracy. Therefore, the thin-film head is expected to become more popular than any other type of perpendicular magnetic head.
Reference is made to FIGS. 7(a) and 7(b) of the accompanying drawings which show by way of example a known thin-film magnetic head for perpendicular magnetic recording, and more particularly, the transducer portion thereof that faces a recording medium. The head comprises a magnetic member 10 formed from, e.g., soft ferrite, a non-magnetic material 3 laid on it and defining a gap layer, a thin-film conductor coil 4 on the material 10 and 3, an insulating layer 5 covering the coil 4, a thick-film magnetic layer 7 formed on the insulating layer 5 of, e.g., a Permalloy, Sendust, or amorphous cobalt alloy, a main pole film 8 formed on the layer 7 which prevents the magnetic saturation of the film 8 during recording, and a protective film 9 formed on the film 8 for protecting the head.
The laminated assembly as hereinabove described has an exposed surface adapted to face a recording medium 30. The magnetic member 10 defines a return path for magnetic flux to the recording medium 30 and has a groove 2 filled with the non-magnetic material 3. The nonmagnetic material 3 and the magnetic member 10 have, however, a boundary plane 12 which is parallel to the main pole film 8, as shown in FIG. 7(a). Therefore, the magnetic flux produced by the main pole returns only to that portion of the medium which faces the main pole, and the head fails to produce a satisfactorily large output for reproduction.
We have previously found that if a laminated film assembly is formed immediately above an intersection of grooves crossing each other at right angles, the return of magnetic flux not only to the area facing the main pole film is achieved, but also along the track width, and thereby an improved output for reproduction is obtained (see Japanese Patent Application No. 50292/1990).
However, such a thin-film head is still unsatisfactory because the magnetic member for the return path is formed from soft ferrite of the Ni-Zn or Mn-Zn series and is too low in hardness to have the necessary resistance to wear caused by the magnetic recording medium which is brought into sliding contact with it.